An LNG storage tank of an LNG carrier generally stores LNG cooled to a temperature of approximately −163° C., and thus is manufactured of a material which may withstand cryogenic temperatures, and has an insulation structure which is strong against thermal stress and thermal contraction and may prevent heat penetration. The LNG storage tank includes a primary barrier, an upper insulation board, a secondary barrier and a lower insulation board which are arranged in turn from an inner side of the storage tank toward an outer side thereof, and is provided to be coupled with an inner hull.
The storage tank has a pump tower for loading and unloading LNG. The pump tower is configured of a pipe structure having a plurality of pipes. The pipes of the pump tower are uprightly installed in a direction passing through an upper surface of the storage tank. At this time, lower portions of the pipes are disposed to face a bottom surface in the storage tank, and upper portions thereof are installed to protrude above the storage tank and to be fixed to a hull.
Generally, each pipe of the pump tower is fixed to an outer hull when fixed to the hull. As an example, Korean Patent Publication No. 10-2011-0026945 (published on Mar. 16, 2011, hereinafter referred to as “a previous document”) discloses a pump tower installation technology in which the upper portions of the pipes are fixed to a trunk deck corresponding to the outer hull and then finished.
However, in this case, since a heat isolating process should be additionally performed in a space formed between the outer hull and the inner hull, a pipe fixing structure and a fixing process may be complicated. Further, since it is difficult to smoothly finish around the secondary barrier disposed between the inner hull and the primary barrier, a leakage problem may occur. Further, since a gas-tight seal portion configured to wrap around the pipes protruding above the outer hull is exposed to an outside of the outer hull, efficiency of adjacent space may be lowered, and the gas-tight seal portion may be easily exposed to various external shocks.